Hey I thought I'd just make these experiment files of mine available - might help somebody

I noticed the SPECIAL_SLAUGHTER is 5+ seconds long and has a lot of "hit points", but when I tried using it it didn't seem to be hitting anything.
Then I noticed, in the .ANIMATION file, the definition for this [ANIMATION] had no [KEY] components whatsoever!
So I tried inserting [KEY]s ("hit", "attack sound" and "effort sound" keys) for each swing in the animation (I used OGRE Mesh Viewer to step through frame-by-frame and see the frame numbers). Saved the new definition into the HUM_M.ANIMATION file and tested it in GUTS.
It worked!

but I haven't attached it to any skill, so I don't know yet if it's hitting like it's supposed to. I think I inserted too many sound [KEY]s tho - it's a NOISY animation!

The new [ANIMATION] definition lines are in the attached archive in the file "SPECIAL_SLAUGHTER_TIMING Animation Definition.txt" which is meant to be added to the .ANIMATION file.
So as not to interfere with the original SPECIAL_SLAUGHTER.SKELETON I made a copy of it and renamed it internally to SPECIAL_SLAUGHTER_TIMING. This .SKELETON file is also in the archive.
The Hum_F model doesn't seem to have the original SPECIAL_SLAUGHTER.SKELETON, so this one I made will only work with the Hum_M model.
Hope this helps someone someday